Process for relaxing internal tensions of textured synthetic yarns



Dec. 1, 197G o T 2 I 3,543,505

PROCESS FOR REIZAX-ING INTERNAL TENSIONS OF TEXTURED SYNTHETIC YARNS. Filed Feb. l7, 1969 g7 f 7 z m s m? M f El fik i Z INVENTOR. @rro 771-08 677/72 3,5435% Patented Dec. 1, 1970 3 543 505 PROCESS FOR RELAYZINC INTERNAL TENSIONS OF TEXTURED SYNTHETIC YARNS Otto Titus Stutz, Wattwil, Switzerland, assignor to Heberlein Patent Corporation, New York, N.Y., a corporation of New York Filed Feb. 17, 1969, Ser. No. 799,676 Claims priority, application Switzerland, Feb. 20, 1968, 2,394/ 68 Int. Cl. 002g 1/02 U.S. Cl. 57-157 6 Claims 4 ABSTRACT OF THE DISCLOSURE This invention relates to treatment of synthetic yarns, and more particularly, to a process for relaxing tensions in such yarns which have been textured by high-twisting same, setting same while in the high twisted condition, untwisting and again heating same.

It is known to produce elastic textured synthetic yarns by temporarily highly twisting thermoplastic multifilament yarns by means of a false-twisting device, for example, and heat-setting the yarns while in the highly twisted state. However, the yarns thus obtained are not suitable for further processing as knitting yarns in order to obtain certain articles of outer and underwear, since their elasticity is too high for that purpose.

Nevertheless, it has been found that the elasticity of yarns treated as mentioned may be reduced by submitting the yarns to a second heat-setting after false twisting. However, it has been found that even after this second heat-setting, sufiicient internal tension remains in the yarns so that, upon drawing-off of the yarn from a bobbin before feeding it to a processing machine, the yarn tends to crinkle. This, in turn, leads to yarn breakages and shutdowns of the machines. It is usual, for this reason, to impart to the yarn a final twist of approximately 60 to 120 turns per meter in the same direction as the direction of the high twist. This measure, though, bears the disadvantage that it involves an extra twist operation on a plytwisting frame whereby the cost of manufacture is substantially increased.

Additionally, a process to relax internal tensions of compensated yarns is known according to which, after initial temporary high-twisting and setting, the yarns are again temporarily high-twisted, but in the opposite direction, and subjected to heat while in the highly twisted state. This process, though, is only suitable for the production of highly elastic yarns and relatively fine yarns of the order to to 40 denier, which are used in the production of womens hosiery and like articles.

Surprisingly, I have found that I am able to relax the internal tensions of synthetic yarns that have been textured by the temporary high-twist and heat set process and the elasticity of which has been reduced by a second heat treatment, by applying a second temporary high-twist to the yarns, but without heat setting in the high-twisted state. This process does not annul the reduction in elasticity or otherwise influence it to any notable extent.

Accordingly, I have conceived by my invention a process for relaxing internal tensions in synthetic textile yarns which have been textured by temporary high-twisting and heat setting while in the high-twisted state, and the clasticity of which has been reduced by a second heat treatment, characterized in that the yarn is submitted to a further temporary high-twisting but in a direction opposite to that of the first high-twisting and without further heat treatment.

I will be appreciated by those persons skilled in the art that by the process of my invention, a special twist step is avoided, i.e., it is replaced by a false twist step which is continuously imparted immediately after texturizing, which process is much simpler and less expensive than twisting on a ply-twisting frame.

According to a variant of the invention, the second temporary high-twist may be imparted while the yarn is in stretched condition. The amount of stretch is selected such that no slip occurs in the twister while breakage is kept to a minimum. These tensions vary according to the material used to make the yarn and to the running speed of the yarn; however, as a rule, favorable results are achieved when the stretch amounts to about 1 to 10 percent.

The process of the present invention is especially suitable for the treatment of textured synthetic multifilament yarns consisting of polyamides, e.g. polyhexamethylene adipamide (nylon 66) or of condensates of epsilon-aminocaproic acid or of ll-aminoundecanoic acid (nylon 6), and of polyesters (polyethylene glycol terephthalate), materials of vinylic base (polyacrylonitrile), or polyolefines. Yarns having total titers of between and 200 denier are preferred.

Several embodiments of the invention have been chosen for purposes of illustration and description, and are shown in the accompanying drawings forming a part of the specification, wherein:

FIG. 1 is a schematic represenation of equipment which may be employed to perform the process of the invention in one of its aspects; and

FIG. 2 is a schematic representation of equipment which may be employed to perform the process in another of its aspects.

The texturization of the yarns may be effected on one of the known false-twist machines. The second heat-setting may be continuously effected directly following the falsetwist operation by using a false-twisting device in which a second-heating device has been provided following the twist imparter. The second heat setting, however, may also be effected in such a way that the yarns are wound onto spools under reduced tension after the false-twist operation and steamed under pressure in an autoclave. In this case, it may be advantageous to eifect the second temporary high-twisting immediately after the first falsetwist operation, i.e., before steaming in the autoclave. The further temporary high-twisting effected following the second heat treatment may also be effected continuously in direct continuation of the first false-twist operation and of the further heat-setting.

Thus. referring to FIG. 1, the yarn 2 coming from the bobbin 1 subsequently runs through a first pair of delivery rollers 3, a heating device 4, a false twist imparter 5 which twists the yarn back through the heating device 4, a second pair of delivery rollers 6, a second heating device 7, a third pair of delivery rollers 8, a second twist imparter 9, a fourth pair of delivery rollers 10 and finally reaches the windup device 11. The heating devices 4 and 7 preferably consist of heated contact surfaces, the twist imparters 5 and 9 rotate in opposite directions, and the rotating speed of the pair of delivery rollers 8 is approximately 10 to 15 percent lower than the speed of the pair of delivery rollers 6, so that the yarn can shrink accordingly during the second heat-setting.

If the second heat-setting is efiected by steaming of the yarn bobbins in an autoclave, it is useful to combine the second temporary high-twisting with a winding operation, i.e., to effect the second false-twist operation on a winding frame. Thus, referring to FIG. 2, the textured yarns 14 and 15 having been delivered from the spools 12, 13, one of which has been temporarily high-twisted in S direction and the other in Z direction may be fed to the false-twist imparters 17, 18, which are driven in opposite direction by means of the belt 16, i.e., the twist imparter 17 in Z direction and the twist-imparter 18 in S direction. The tWo yarns 14 and 15 are then separately wound onto the bobbins 19 and 20, respectively.

In the second false-twist operation, either a twist imparter used in the usual false-twist texturing machines such as a twist tube or a friction twist imparter may be used.

The process of the invention is hereinafter described in more detail by means of some examples:

EXAMPLE I A multifilament yarn of nylon 66 having a titer of 70 denier and consisting of 34 filaments, which has an initial twist of between 15 and 20 turns per meter in S direction is high-twisted to 3000 turns per meter in S direction and led over a heated surface having a temperature of 230 C., to heat set the yarn in the high-twisted condition. The thread-forwarding means of the machine are thus arranged that the yarn undergoes a 2 percent shrinkage during false-twisting and heat-setting. The yarn is then wound up by feeding to the windup device at a speed which exceeds the peripheral speed of the same by 20 percent. Thereafter, the yarn is steamed in the wound-up state in an autoclave at a pressure of approximately 2.5 atmospheres gauge. The yarn is then temporarily high-twisted to 2750 turns per meter by means of a second false-twist device, the thread-feeding devices of the machine being so arranged that the yarn undergoes stretching of ap proximately 3.5 percent. The so treated yarn presents a reduced elasticity and simultaneously the internal tensions are substantially fully relaxed.

EXAMPLE II A multifilament yarn consisting of polyethylene glycol terephthalate having a titer of 150 denier, consisting of 30 filaments and having an initial twist of 15 to 20 turns per meter in S direction, is temporarily high-twisted to approximately 2000 turns per meter in Z direction by means of the false-twist device shown in FIG. 1, i.e., by means of the twist-imparter 5, and heat-set in the hightwisted state during 0.65 second by hot air contained in the heating device 4. During false-twisting and heat setting, shrinkage of the yarn by approximately 4 percent takes place. The yarn is then subjected to a second heatsetting at 190 C. in the heating device 7 consisting of a heated contact surface, wherein it undergoes a shrinkage of approximately 12 percent between the thread-forwarding devices 6 and 8. Thereupon, the yarn is temporarily high-twisted to 2400 turns per meter in S direction, whereby the thread-forwarding devices 8 and are so arranged that the yarn undergoes stretching of approximately 4 percent. The thus obtained textured yarn presents reduced elasticity and simultaneously the internal tensions are substantially fully relaxed.

EXAMPLE III A :multifilament yarn consisting of nylon 66 having a titer of approximately 100 denier, consisting of 34 filaments and having an initial twist of approximately between and turns per meter Z is treated by means of a false-twist device according to FIG. 1, wherein a first temporary high-twisting up to 2600 turns per meter and a first heat-setting by hot air of 210 C. is eifected under shrinkage of the yarn by approximately 2 percent. The second heat setting of the yarn is effected by means of the contact surface 7 heated to 225 0, whereby the yarn undergoes shrinkage of approximately 12 percent. The yarn is then subjected to a second high-twisting operation to 2.800 turns per meter in Z direction thereby undergoing a stretch of approximately 9 percent. The thus obtained textured yarn presents reduced elasticity and simultaneously the internal tensions are substantially fully relaxed.

From the foregoing description it will be seen that I contribute a process for relaxing the internal tensions of synthetic yarns which have been textured by hightwisting and heat-setting same while in the high-twisted state, and which have then had a further heat treatment to reduce elasticity.

I believe that my novel process will now be fully understood and that its advantages will be appreciated by those persons skilled in the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the relaxation of the internal tensions of synthetic textile yarns which have been textured by temporary high-twisting and heat-setting in the hightwisted state, the elasticity of which has been reduced by a subsequent second heat-setting operation, characterized in that the textile yarn is subjeced, after the temporary high-twisting, to a further temporary high-twisting in opposite direction.

'2. A process according to claim 1, further characterized in that the second temporary high-twisting is efiected while the yarn is stretched.

3. A process according to claim 2, further characterized in that the yarn is stretched by an amount of between 1 and 10 percent during the second temporary high-twistmg.

4. A process according to claim 1, further characterized in that the second temporary high-twisting is effected continuously directly following the first temporary high-twisting and the second heat-setting, by efiecting the operations on a false-twist machine having two false-twisters with a heater arranged therebetween.

5. A process according to claim 1, further characterized in that the second high-twisting is accomplished in connection with a wind-up operation effected following the second heat-setting treatment, by performing the second twisting and the wind-up steps on a wind-up machine equipped with a false-twister.

6. A process according to claim 1, further characterized in that the second temporary high-twisting is accomplished immediately after the first temporary high-twisting and before the second heat-setting operation by means of steam at a gauge pressure exceeding 1 atmosphere.

References Cited UNITED STATES PATENTS 2,475,922 7/1949 Stockly 5734 3,091,912 6/1963 Stoddard et a1. 57l57 XR 3,137,119 6/1964 Crouzet 57-157 3,165,881 1/1965 Moncuit et al. 5734 3,166,881 1/1965 Servage 5734 3,318,083 5/1967 Gilcrist 57-34 XR 3,367,096 2/1968 Comer et a1. 57--34 3,438,190 3/1969 Collingwood 57157 XR DONALD E. WATKINS, Primary Examiner 

